This invention relates to mass transit vehicle lighting systems; more particularly, it relates to a lighting system for the passenger compartment of a bus using light pipes.
Lighting systems for passenger seating areas in mass-transit vehicles frequently include a plurality of fluorescent lamps arranged in rows. Each row of lamps is commonly enclosed within an elongated channel that forms part of an elongated lamp housing. The elongated channel may be connected to or integrally formed with an elongated display panel for holding advertising cards. A lamp housing of this type will also typically include an elongated translucent or transparent light cover disposed across the open side of the channel to aid in controlling the distribution of light emitted from the lamps.
Together, the lamp housing and display panel make up an elongated light fixture. Such light fixtures are typically manufactured in long sections that mount end-to-end in the cornice areas above the passenger seating areas and above the vehicle side windows in mass-transit vehicles. U.S. Pat. No. 4,574,336 issued Mar. 4, 1986 to Mikalonis and U.S. Pat. No. 4,387,415 issued Jun. 7, 1983 to Domas disclose lighting systems of this type.
Fluorescent vehicle lighting systems are inherently difficult to service and require a considerable amount of maintenance. Fluorescent lamps frequently bum out and require replacement. When lighting systems use large numbers of lamps, the odds that one of the lamps will burn out over a given period of time increases. Therefore, the larger the number of lamps that a lighting systems uses, the more often that system will require bulb and ballast replacement.
Lighting systems that use multiple lamps also require multiple lamp sockets and complex wiring harnesses. Wiring harnesses for multiple-lamp lighting systems must connect every lamp socket to an electrical power source. In addition, the lighting fixtures housing the lamps and ballast must be designed to allow easy access for replacing, lamps and ballast.
Systems using multiple lamps inherently leave xe2x80x9cdark spotsxe2x80x9d between lamps. Rows of fluorescent lamps oriented end-to-end leave dark spots where the ends of each lamp plug into a socket and no light is emitted. The dark areas between the lamps are difficult to minimize without extending the lengths of the lamps.
When confronted with applications requiring linear light sources, designers have sometimes turned to fiber optics. Advances in fiber optic technology have made it possible to manufacture linear light sources that can efficiently distribute light both laterally from their circumferences as well as longitudinally from their ends. This type of product is known as a xe2x80x9cside-lightxe2x80x9d or xe2x80x9cside-firexe2x80x9d optic or a xe2x80x9cside-firexe2x80x9d light pipe.
Lumenyte International Corporation manufactures a xe2x80x9cside-firexe2x80x9d light pipe that includes a solid acrylic core with either a circular or an oval cross-section. The diameter of the core is approximately one-half of an inch. A Teflon(copyright) cladding surrounds the core and has an index of refraction that causes the light pipe to emit light laterally. A clear jacket surrounds the cladding to reflect a certain amount of light back into the core.
Also available from Lumenyte International Corporation is the LUMENYTE(copyright) STARBURST(trademark) OPTICxe2x80x94a side-fire light pipe with small angled cuts along its length. The cuts create optical discontinuities along the length of the light pipe that increase the amount of light emitted laterally. The depth, angle and spacing of these cuts can be varied to customize light distribution to suit a particular application.
The prior art also includes fiber optic lighting systems that have been proposed for use in vehicular applications. An example of a proposed vehicular application of fiber optic technology is described in U.S. Pat. No. 4,947,293 issued to Johnson et al. The Johnson et al. patent discloses a clearance lighting system for a semi trailer cargo container body. The system includes a light source that end-illuminates elongated light-conducting strips. The strips are supported along both sides of a container body and emit light both longitudinally and laterally. Another Johnson patent, U.S. Pat. No. 5,122,933, discloses a similar fiber optic lighting system that includes a message panel. However, the lighting systems disclosed in the later two patents are not adapted to preferentially distribute light into the passenger seating area of a mass transit vehicle.
Another example of a vehicular application for fiber optic technology is. disclosed in U.S. Pat. No. 4,740,870 issued to Moore et al. The Moore et al. patent discloses a fiber optic lighting system for boats. The system includes a plurality of xe2x80x9cend-firexe2x80x9d fiber optic cables that each receive light at one end from a central light source. The cables conduct light longitudinally to light fixtures located at remote locations within a boat.
Two other examples are disclosed in U.S. Pat. No. 4,811,172 to Davenport et al. and U.S. Pat. No. 5,184,883 to Finch et al. Each of these patents discloses a fiber optic lighting system for motor vehicles. The systems include a light source that end-illuminates a plurality of fiber optic filaments. The filaments conduct the light longitudinally to the vehicle head and tail lamp fixtures.
There remains a need for lighting systems that can supply sufficient illumination to meet lighting requirements in passenger seating areas of mass-transit vehicles while reducing the amount of lamps, wiring and maintenance that current systems require.
In accordance with this invention, an improved lighting system is provided for illuminating a passenger seating area in a mass transit vehicle. The improved system replaces fluorescent tubes with one or more optically coupled light pipes. The light pipes extend between elongated lamp housing sections and the passenger seating area to preferentially distribute light into the passenger seating area while reducing the amount of lamps and maintenance required.
Light pipes may be formed into segments much longer than a fluorescent tube thus minimizing the number of xe2x80x9cdark spotsxe2x80x9d along the length of a light fixture. Because they conduct light, several shorter light pipes may be arranged end-to-end, in series, to extend from a single light source. Consequently, with the exception of the light source, there are no lamps to burn out and require replacement. Such a system does not need complex wiring harnesses because there are fewer lamps and therefore fewer lamp sockets requiring electrical power. Moreover, light sources for illuminating light pipes can be selected that do not require the heavy inverter ballasts that fluorescent lamps require.
According to another aspect of this invention, a lighting system is provided which can be used with either light pipes or fluorescent lamps. The system includes a plurality of light fixtures, each having a pair of end caps disposed at either end of an elongated lamp housing. Each end cap may include either a D-shaped through hole to receive a fluorescent bulb socket or a circular hole to receive a light pipe.
According to another aspect of this invention, an elongated mounting fin integrally and laterally extends from along the length of each light pipe. Each mounting fin either snaps laterally or slides longitudinally into an elongated slot in a lamp housing section. Each fin supports the light pipe it extends from without interrupting the light that the light pipes emit into the seating area.
According to another aspect of this invention, each light fixture additionally includes an air duct extension panel. Each air duct extension panel is adapted to mount between the vehicle side wall and a face panel to space the face panel from the side wall. Each air duct extension panel has an inner edge connected to the face panel lower edge, and an outer edge connected to the vehicle side wall.
According to still another aspect of this invention, each lamp housing section is formed together with one of the air duct extension panels in a position adjacent and generally parallel to the air duct extension panel inner edge. Each face panel is detachably connected along its lower edge to a corresponding duct extension panel. This configuration allows the face panel to be removed from the light fixture without, at the same time, removing the lamp housing from the light fixture.
According to another aspect of the invention, a light pipe hanger device is provided for suspending a light pipe from a supporting structure in, for example, a light fixture. The device comprises a band of resilient material that includes a lower hoop. The lower hoop is configured to wrap around the light pipe to be suspended. A connector is attached to the lower hoop and is configured to fasten the hanger device to the supporting structure. Unlike prior art hangers the connector comprises an upper probe portion that integrally extends from the lower hoop and is configured to engage an opening in the supporting structure to suspend the hanger device and the light pipe from the supporting structure.
According to another aspect of the invention, the lower hoop and the upper probe portion of the hanger device are a single unitary piece.
According to another aspect of the invention, the device includes a resilient portion configured to allow the upper probe portion to compress sufficiently to pass upward through the opening and to spring back toward a relaxed shape. The relaxed shape allows the probe portion to engage a rim defining the opening in the supporting structure and to resist being pulled back downward through the opening.
According to another aspect of the invention, the lower hoop is a band of the resilient material.
According to another aspect of the invention, the device comprises a length of spring metal bent to form the lower hoop and upper probe portions.
According to another aspect of the invention, the device comprises a plastic material. The plastic material may be translucent or transparent to preclude the device from blocking light radiating from a side-fire light pipe.
According to another aspect of the invention, the upper probe portion comprises an arcuate lobe. The arcuate lobe and lower hoop together form a closed arcuate band having the general shape of a pair of opposing lobes integrally merging at a pinched region. The arcuate lobe is broader than the opening in the supporting structure and is laterally compressible to fit through the opening when pushed upward through the opening.
According to another aspect of the invention, the lower hoop includes a circumferential gap configured to receive the light pipe in snap-in engagement. The snap fit feature provides a quick and easy method for installing light pipes in the light fixture.
According to another aspect of the invention, the upper probe portion comprises a mounting fin that includes a stem extending integrally upward from the lower hoop of the light pipe hanger. The stem is disposable within the opening in the supporting structure. The mounting fin additionally includes a first engagement surface disposed adjacent the stem. The first engagement surface is configured to engage the supporting structure once the mounting fin has been pushed through the opening.
According to another aspect of the invention the fin includes a second engagement surface disposed adjacent the stem. The first and second engagement surfaces are disposed on laterally opposite sides of the stem and together provide greater stability.
According to another aspect of the invention, the fin includes an apex defining a fin upper edge. In addition, a pair of ramp surfaces tapers outward and downward from the apex to an outer edge of each of the fin engagement surfaces to form a pair of barbs.
According to another aspect of the invention, the stem is sufficiently narrower than the opening. This is to allow the barbs to fit through the opening with the stem by folding against the stem. Once the fin is through the opening, the barbs will xe2x80x9cdeployxe2x80x9d into a position that they cannot easily be drawn back down
According to another aspect of the invention a method is provided for installing a light pipe in a light fixture using the above hanger device. The method includes inserting the fin upper edge upward into the opening in the lamp-support panel with the fin ramp surfaces engaging a rim defining the opening in the lamp support panel, forcing the fin through the opening such that contact with the rim causes the elongated barbs to first compress inward against the elongated stem and to then spring back outward after passing through the opening with the barbs spread-out across the opening, and snapping a light pipe into the lower hoop by pushing the light pipe sideways through the gap in the lower hoop.
According to another aspect of the invention, opposite ends of the band of resilient material are drawn together and crossed forming the lower hoop. The upper probe portion comprises opposite terminal lengths of the band extending diagonally upward and outward from a cross point where the two terminal lengths cross. Each terminal length additionally includes an engagement surface configured to engage the supporting structure when the upper probe portion has been moved through the opening in the supporting structure.
According to another aspect of the invention, the hanger device band has a relaxed state in which the terminal lengths are crossed. In the relaxed state, the distance between the crossed ends of the band is greater than a distance across the opening. In addition, in the relaxed state, the lower hoop may have a diameter less than a diameter of a light pipe to be suspended in the hoop.
According to another aspect of the invention, a method is provided for installing the above light pipe in a light fixture. The method includes expanding the lower hoop of the hanger such that the upper ends of the probe prongs move close enough together to pass through the opening in the lamp-support panel, inserting the upper ends of the probe prongs through the opening, releasing the lower hoop to allow the hoop to contract back toward a pre-expanded/relaxed position in which the upper ends of the probe prongs are spread far enough apart to engage opposing sides of a rim defining the opening and suspending the hanger from the lamp-support panel and inserting the light pipe axially through the lower hoop to suspend the light pipe and to prevent the hoop from closing, pulling the prongs together and releasing the light pipe.
According to another aspect of the invention, from the cross point each as terminal length extends diagonally upward and outward then forms a detent configured to engage opposite edges of the opening. The detent engages the edges when the upper probe portion has been moved partially through the opening. The terminal lengths are inwardly compressible to a compressed position that allows the terminal lengths to pass through the opening in the supporting structure.
According to another aspect of the invention, each detent comprises a generally vertical section of one of the terminal lengths that integrally extends in a generally vertically upward direction from an upper end of the diagonally extending portion of that terminal length. The generally vertical sections of the terminal lengths may also include generally arcuate intermediate portions having generally concave surfaces that face laterally outward and are configured to engage the opposite edges of the opening when the upper probe portion has been moved partially through the opening.
According to another aspect of the invention, each terminal length of the band includes a diagonally inwardly and upwardly extending upper ramp that integrally extends from an upper end of the intermediate portion of the terminal length. Each upper ramp has an engagement surface configured to aid in guiding the upper probe portion into the opening. The upper ramps allow an operator to push the upper probe portion into the opening without having to first squeeze or compress the terminal lengths together.
According to another aspect of the invention, a method is provided for installing a light pipe in a light fixture. The method includes placing the prongs in contact with opposing sides of a rim defining the opening in the lamp-support panel, pushing the hanger device upward until the prongs engage opposing the sides of the rim and the lower hoop is expanded sufficiently to receive the light pipe, inserting the light pipe axially through the expanded lower hoop of the hanger device, pushing the hanger device farther upward until the prongs disengage from the rim, move upward through the opening and splay upward and outward over the lamp-support panel as the lower hoop closes inward around the light pipe.
According to another aspect of the above method, an upper engagement surface of a ramp portion of each prong is initially placed in contact with opposing sides of the rim. Pushing the hanger device upwards causes the prongs to move inward toward each other as the ramp portions slide upward along the opposite sides of the rim. The hanger device is pushed upwards until detent portions of the prongs engage the rim, holding the lower hoop open for light pipe insertion. Once a light pipe has been inserted, the hanger device is pushed upward until the detent portions disengage from the rim. This arrangement provides a quick and easy way for an installer to install a light pipe in a light fixture.
According to another aspect of the present invention, the lighting system includes a dual-port light source mounted in the vehicle. First and second elongated light pipes each have an input end optically coupled to the light source to receive light therefrom. The light pipes extend from the light source in generally opposite directions above the seating area adjacent the lamp housing. Each dual-port light source reduces by one the number of light sources required to illuminate the light fixture without an excessive loss of lateral illuminating power at portions of the light pipe/pipes remote from the light source/sources.
To better understand and appreciate the invention, refer to the following detailed description in connection with the accompanying drawings: